Mineral Spectral Mapping of Chlorite–Muscovite: Locating Concealed Mineralization in the Dahongshan Cu‐Fe Deposit in Central Yunnan, Southwest China

ABSTRACT The Dahongshan Cu‐Fe deposit is located within the central Yunnan uplift, bordered by the Honghe and Lüzhijiang faults. It exemplifies a typical stratabound‐hydrothermal reworked deposit within the Kangdian Cu‐Fe metallogenic belt, situated on the western margin of the Yangtze Block. This study focused on the 60 m elevation above sea level. Using short‐wave infrared (SWIR) spectroscopy, we analysed the spectral parameters of alteration minerals, primarily the chlorite group and muscovite. Spatial distribution models were developed through mineral spectral mapping to quantify the relationship between alteration minerals and copper grades. Key findings include: (1) Copper grades exceed the industrial cut‐off grade of 0.2 wt% in zones corresponding to moderate to high relative spectral index values of chlorite‐group minerals. (2) High chlorite spectral peak intensity zones are spatially coincident with high‐grade Cu mineralization, reflecting the paragenetic association of chlorite and sulphides in hydrothermal fluid pathways. (3) Muscovite crystallinity is on average lower in ore‐proximal zones than in surrounding wall rock. This distinct difference reflects Cu mineralization–related hydrothermal alteration, which induces muscovite lattice distortion and consequent crystallinity reduction in ore‐bearing hydrothermal fluid zones. In conclusion, the spatial distribution of chlorite content, its spectral characteristics, and the pattern of muscovite crystallinity attenuation provide essential geological‐spectral criteria for predicting concealed ore bodies within the Dahongshan Cu‐Fe deposit.